Re: [PATCH] PM / Clocks: fix pm_clk_resume/suspend if CONFIG_PM_RUNTIME is set

[Grygorii Strashko <grygorii.strashko@ti.com>]

Hi Stephen,

On 11/20/2013 08:42 PM, Stephen Boyd wrote:
> On 11/20/13 05:31, Grygorii Strashko wrote:
>> The following warning is shown and clk_enable() failed on Keystone platform
>> if CONFIG_PM_RUNTIME is set and Runtime PM is enabled for Davinci gpio driver:
>> [    0.564486] ------------[ cut here ]------------
>> [    0.569221] WARNING: CPU: 0 PID: 1 at drivers/clk/clk.c:883__clk_enable+0x8c/0x98()
>> [    0.577070] Modules linked in:
>> [    0.580231] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.12.0-10116-g11d59938-dirty #259
>> [    0.588368] [<c0014d34>] (unwind_backtrace+0x0/0xf8) from [<c0011eb8>] (show_stack+0x10/0x14)
>> [    0.597018] [<c0011eb8>] (show_stack+0x10/0x14) from [<c03c5df0>] (dump_stack+0x64/0xa4)
>> [    0.605235] [<c03c5df0>] (dump_stack+0x64/0xa4) from [<c00216b8>] (warn_slowpath_common+0x68/0x88)
>> [    0.614315] [<c00216b8>] (warn_slowpath_common+0x68/0x88) from [<c00216f4>] (warn_slowpath_null+0x1c/0x24)
>> [    0.624092] [<c00216f4>] (warn_slowpath_null+0x1c/0x24) from [<c0287a60>] (__clk_enable+0x8c/0x98)
>> [    0.633173] [<c0287a60>] (__clk_enable+0x8c/0x98) from [<c0287c54>] (clk_enable+0x18/0x2c)
>> [    0.641556] [<c0287c54>] (clk_enable+0x18/0x2c) from [<c023677c>] (pm_clk_resume+0x5c/0x80)
>> [    0.650025] [<c023677c>] (pm_clk_resume+0x5c/0x80) from [<c001eba8>] (keystone_pm_runtime_resume+0xc/0x18)
>> [    0.659800] [<c001eba8>] (keystone_pm_runtime_resume+0xc/0x18) from [<c02344e4>] (__rpm_callback+0x34/0x70)
>> [    0.669662] [<c02344e4>] (__rpm_callback+0x34/0x70) from [<c0234548>] (rpm_callback+0x28/0x88)
>> [    0.678390] [<c0234548>] (rpm_callback+0x28/0x88) from [<c023590c>] (rpm_resume+0x3c8/0x684)
>> [    0.686942] [<c023590c>] (rpm_resume+0x3c8/0x684) from [<c0235e40>] (__pm_runtime_resume+0x4c/0x64)
>> [    0.696111] [<c0235e40>] (__pm_runtime_resume+0x4c/0x64) from [<c0204798>] (davinci_gpio_probe+0x20c/0x5ac)
>> [    0.705983] [<c0204798>] (davinci_gpio_probe+0x20c/0x5ac) from [<c02310cc>] (platform_drv_probe+0x18/0x48)
>> [    0.715758] [<c02310cc>] (platform_drv_probe+0x18/0x48) from [<c022fa0c>] (driver_probe_device+0x80/0x21c)
>> [    0.725532] [<c022fa0c>] (driver_probe_device+0x80/0x21c) from [<c022fc34>] (__driver_attach+0x8c/0x90)
>> [    0.735044] [<c022fc34>] (__driver_attach+0x8c/0x90) from [<c022e35c>] (bus_for_each_dev+0x60/0x94)
>> [    0.744207] [<c022e35c>] (bus_for_each_dev+0x60/0x94) from [<c022f24c>] (bus_add_driver+0xdc/0x1d0)
>> [    0.753371] [<c022f24c>] (bus_add_driver+0xdc/0x1d0) from [<c023002c>] (driver_register+0x78/0xf4)
>> [    0.762449] [<c023002c>] (driver_register+0x78/0xf4) from [<c00088fc>] (do_one_initcall+0xec/0x148)
>> [    0.771616] [<c00088fc>] (do_one_initcall+0xec/0x148) from [<c0538c0c>] (kernel_init_freeable+0xfc/0x1c8)
>> [    0.781303] [<c0538c0c>] (kernel_init_freeable+0xfc/0x1c8) from [<c03c19d0>] (kernel_init+0x8/0x110)
>> [    0.790553] [<c03c19d0>] (kernel_init+0x8/0x110) from [<c000e318>] (ret_from_fork+0x14/0x3c)
>> [    0.799117] ---[ end trace 6588a0ec7fbc847a ]---
> 
> Please omit the timestamps here.

ok.

> 
>>
>> This happens because the clk_enable() is called without clk_prepare()
>> from pm_clk_resume().
>>
>> Hence, switch to use clk_prepare_enable()/clk_disable_unprepare()
>> instead of clk_enable()/clk_disable() in case if CONFIG_PM_RUNTIME is
>> set.
>> Actually, This is remainder fix of the earlier commit c122f27e1c
>> "base: power - use clk_prepare_enable and clk_prepare_disable".
>>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
>> ---
>>   drivers/base/power/clock_ops.c |    4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
>> index 9d8fde7..60d389a 100644
>> --- a/drivers/base/power/clock_ops.c
>> +++ b/drivers/base/power/clock_ops.c
>> @@ -230,7 +230,7 @@ int pm_clk_suspend(struct device *dev)
>>   	list_for_each_entry_reverse(ce, &psd->clock_list, node) {
>>   		if (ce->status < PCE_STATUS_ERROR) {
>>   			if (ce->status == PCE_STATUS_ENABLED)
>> -				clk_disable(ce->clk);
>> +				clk_disable_unprepare(ce->clk);
>>   			ce->status = PCE_STATUS_ACQUIRED;
>>   		}
>>   	}
>> @@ -259,7 +259,7 @@ int pm_clk_resume(struct device *dev)
>>   
>>   	list_for_each_entry(ce, &psd->clock_list, node) {
>>   		if (ce->status < PCE_STATUS_ERROR) {
>> -			clk_enable(ce->clk);
>> +			clk_prepare_enable(ce->clk);
>>   			ce->status = PCE_STATUS_ENABLED;
>>   		}
>>   	}
> 
> This is inside a spin_lock_irqsave(). You should be getting scheduling
> while atomic warnings with this change. Are you testing with
> DEBUG_ATOMIC_SLEEP=y?

Ops, thanks. No, It's not tested with DEBUG_ATOMIC_SLEEP and 
I agree with you.

So, I see two option here:
1) split above loops on two
2) add calls of clk_prepare()/clk_unprepare() in pm_clk_notify()

In my opinion option [2] is better.

Regards,
-grygorii